While the present invention is directed to a composite sheet for application to the surface of skin for delivering therapeutic agents to the skin, a preferred embodiment will be described showing the delivery of therapeutic agents to the surface of the skin for treating wounds, cuts, burns and scar tissue.
Typically, when the skin is traumatized, cut or burned, scar tissue will form. In some instances the scar tissue may comprise a large area and may become prominent. The scar tissue may discolor or become darkened, become hypertrophic and protrude from the surface of the skin making it more noticeable. It may overgrow the boundaries of the initial area of injury and continue to grow or form a keloid. If the scar tissue happens to cover a joint, the movement of the joint may become restricted and extremely painful.
The severity of the scarring may be affected by many factors including the dimensions of the wound, the blood supply to the wound area, the thickness and color of the skin, and the orientation of the scar. Further, the age of the victim may also affect the scar formation. In younger individuals, this can and may result in larger, thicker scars in comparison to an older individual.
There are several methods available for treating and reducing keloid and hypertrophic scars. Surgical excision has been used for a number of years and has also been proved to be ineffective in a large number of cases due to the recurrence of scar tissue. The surgery requires removal of the scarred skin and rejoining the normal skin in a manner such that the wounded area is less apparent. This type of treatment is fairly expensive, and since it is surgery, there is the possibility of complications.
Dermal abrasion (dermabrasion) is also used to smooth scar tissue by scraping or shaving off the top layers of the skin using surgical devices. The activity is often successful in leveling the irregularities of the surface scars, however, the procedure is painful and multiple treatments may be required. Given that this is a surgical procedure, the concerns raised above are valid and the potential for complications, including hypertrophic and keloid scars still exists.
Other treatments for scar tissue involve the use of injectable fillers such as collagen or fat, which are injected below the depressed scar tissue to elevate it and have it appear to be level with the surrounding skin. Continuous treatments may be required because the results are not always permanent. These agents cannot be used for elevated scars.
Other therapeutic treatments for scar tissue include occlusive dressings, compression therapy, intralesional corticosteriod injections, cryosurgery, radiation therapy, laser therapy and interferon therapy.
Silicone gels in the form of sheets have been widely used in the management of new scar tissue and hypertrophic keloid scarring. The silicone sheets are typically applied with pressure against scar tissue so the formation of hypertrophic scar tissue and attendant coloration can be reduced resulting in a more normal appearance. Typically the silicone sheets are better than traditional bandages because the gel adapts itself to the contours of the body. While the use of silicone dressings may be somewhat effective in the treatment of new scar tissue, the occlusive effects of the silicone sheets may be associated with infection due to the accumulation of microbes on the skin.
U.S. Pat. No. 6,572,878 describes a method for minimizing the appearance of scars comprising the application of a semi-occlusive device to a closed wound on the skin wherein the device comprises one layer of silicone sheet infused with an antioxidant and an antimicrobial. The device is used on the surface of the skin and reapplied daily for up to thirty days.
U.S. Pat. No. 6,472,581 describes a silicone sheet, which is formed by a silicone gel layer with a silicone elastomer layer. The elastomer layer is formed by curing a silicone elastomer composition obtained by adding a silicone cross-linking compound to an addition reaction carrying silicone gel composition.
U.S. Pat. No. 6,159,494 describes a method for treating scars by applying a microporous tape to the scar tissue containing panthenol, which serves as a contact medium for allowing a therapeutic agent to pass there through to the surface of the skin. Typically a hydrating agent is used that is derived from the plant Bulbine frutesences. 
U.S. Pat. No. 5,919,476 describes a bandage in the form of a reinforced silicone gel sheet for application to scar tissue. The bandage comprises three layers; a tacky skin contacting first layer made from a silicone sheet, a reinforcing second layer comprising a non-liquid permeable mesh fabric support structure having a plurality of holes therethrough and a non-tacky bonding third layer which includes the holes and laminates itself to the first layer, thereby securing the second layer between the first and third layer.
U.S. Pat. No. 5,895,656 describes a gas or gel filled silicone bandage made of silicone sheeting. The flexible silicone sheeting or film contains an interior space that may be filled with dry gas or a hydrophobic gel. Since there is reduced electrical resistance in the scar tissue, the use of the hollow space in the bandage may increase the static electrical field or negative charge applied to the scar which could hasten the inhibitatory healing process for hypertrophic and keloid scars. To improve the electric field within the hollow space, small pieces of Teflon™ sheeting or silicone beads may be inserted in the hollow space.
U.S. Pat. No. 5,759,560 describes a silicone thermal plastic sheeting for scar treatment which has two layers, a first layer of a therapeutic agent to be placed on to the skin and a second backing layer of a thermoplastic polymer bonded to the first layer to provide a thick shape to the material.
U.S. Pat. No. 6,284,941 describes a bandage for treatment of scar tissue comprising a flexible and breathable member having first and second sides with an adhesive located on the first side and a scar treatment pad attached to the first side of the flexible member. The scar treatment pad comprises a layer of silicone elastomer adhesively attached to the center area of the first side of the flexible member so that the adhesive borders are located on lateral sides of the scar treatment pad. The flexible member is non-occlusive.
The foregoing patents describe methods of applying silicone to the surface of skin for treating scar tissue, however, as previously stated, the devices are typically occlusive, or if they are non-occlusive, do not provide for additional application of therapeutic agents. Therefore, there is a need for a device and method for applying therapeutic agents to the skin and treating scar tissue including minimizing the appearance of hypertrophic and keloid scars.
Therefore, it is the object of the present invention to provide a device or composite sheet for delivering therapeutic agents to the surface of the skin.
It is another object of the present invention to provide a device or composite sheet for treating scar tissue.
It is a further object of the present invention to provide a device, which can be applied to the surface of the skin for long periods of time, up to fourteen to thirty days.
It is another object of the present invention to provide a device or composite sheet to be applied to the surface of the skin for preventing and treating scar tissue.
It is another object of the present invention to provide a device or composite sheet to be applied to the surface of the skin for treating acute scars.
It is another object of the present invention to provide a polymer foam material for holding and releasing a therapeutic agent encapsulated in a polymer enrobing material which is in contact with the skin which holds and releases the therapeutic agent on to the skin.
It is another object of the present invention to provide a device or composite sheet to be applied to the surface of the skin for the treatment of non-traumatized skin and for the modulation of the scar forming process through all phases of healing.
It is another object of the present invention to provide a device or composite sheet to be applied to photoaged skin.
It is another object of the present invention to provide a device or composite sheet to be applied to open wounds.
It is another object of the present invention is to provide a composite material containing a plurality of microchannels which pass through a polymer enrobing material and a polymer foam material for holding and releasing a therapeutic agent onto the surface of the skin.
Other objects and advantages will become apparent upon reading the specification of the appendant claims.